To improve the effectiveness of drug therapy and to reduce possible systematic side effects, many attempts have been made to deliver drugs in a controlled profile to human patients. The advantage of controlled release dosage forms are well-known in both the pharmaceutical and medical sciences. The therapeutical benefits of controlled-release dosage forms include the pharmacokinetic ability to maintain a preplanned blood level of an administered drug over a comparatively longer period of time. The therapeutical benefits include also a simultaneous increase in patient compliance and a reduction in the number of doses of drug administered to a patient.
The prior art made available controlled release dosage that sought to provide a drug release rate profile that matched the blood physiological and chrono-pharmacological requirements needed for therapy. For example, U.S. Pat. Nos. 3,845,770 and 3,916,899 issued to Theeuwes and Higuchi pertains to an osmotic dosage form for delivering various drugs to a patient environment of use. The dosage forms disclosed in these patents are manufactured comprising a wall that surrounds a compartment comprising a drug with an exit in the wall for delivering the drug to a patient. In U.S. Pat. Nos. 4,008,719; 4,014,334; 4,058,122; 4,116,241; and 4,160,452 patentees Theeuwes and Ayer made available dosage forms comprising an inside and an outside wall made of poly(cellulose acylate) for delivering a dosage of drug to a patient in need thereof.
The history of the prior art dosage forms indicates a serious need exists for a novel and useful dosage form that provides an unexpected advancement in the science of dosage forms. For example, the prior art dosage forms lack the present ability to mask an unpleasant taste, they did not maintain the stability of a drug formulation, and the dosage forms did not protect a drug from oxidation. Then too, the drug formulation in the dosage form permitted the drug release profile to decline over time, thereby administering a nontherapeutic dose of drug. The wall of the dosage forms exposed to the gastrointestinal tract were lipophilic, they absorbed endogenous fats and consequently evidenced a decrease in structural integrity as seen in flaws or cracks in the wall. Moreover, the dosage forms wall and its drug formulation did not act in concert for providing a controlled linear drug delivery profile over an extended time. Likewise, prior art dosage forms were formulated with water-leachable components within the membrane to control delivery rate of drug which water-leachable components diffused from the membrane against the direction of osmotic water flux making reproducibility and control of delivery rate patterns difficult, as seen in U.S. Pat. No. 5,160,744.
It is clear from the above presentation that a long-felt need exists for a dosage form comprising a walled structure and a drug formulation that function together for administering orally a drug at a controlled and sustained-release drug delivery profile with time. The need exists for a dosage form for administering a drug in a linear profile for treating infectious diseases, respiratory diseases, the cardiovascular system, blood and spleen, the digestive system, metabolic disorders, the endocrine system, the urogenital tract, sexually transmitted diseases, the nervous system, the locomotor system, psychiatric disorders and for providing symptomatic care. A dosage form is needed for replacing immediate-release dose-dumping forms administered three or four times daily. There are serious reasons for seeking a dosage form that replaces immediate-release forms, including a means for reducing peak-blood levels followed by a sharp drop in blood levels, a means for lessening side effects, a means for manufacturing the structural integrity of the dosage form, and a means for reducing the number of solvents used to manufacture the dosage form.